Encoding:
    SILC_ASN1_INT(integer)
    SILC_ASN1_INT_T(opts, tag, &integer)

    Decoding:
    SILC_ASN1_INT(&integer)
    SILC_ASN1_INT_T(opts, tag, &integer);

    Macro used to encode or decode multiple precision integer.  The
    integer type is SilcMPInt.

    The `opts' is SilcAsn1Options.  The `tag' is a tag number.